Purpose

To establish a linear measuring method in computed tomographic (CT) images to predict the displacement of the globe late after orbital blowout fracture.

Methods

Subjects were retrospectively included. Inclusion criteria were as follows: (1) adult subjects (≥18 years old at the time of trauma); (2) unilateral orbital medial‐wall and/or floor fractures; (3) CT examination at least 30 days after trauma. Exclusion criteria were as follows: (1) facial or orbital fracture extending to other parts of the orbit than medial‐wall and/or floor; (2) history of orbital or ocular abnormality other than the orbital trauma; (3) severe ocular trauma accompanied by the orbital trauma; (4) orbital fracture treated surgically before the CT examination. A co‐ordinate system was built based on the orbital CT scans. Displacements of orbital walls, displacement of the globe and relative location of the fracture site were measured. Correlations between the variables were investigated.

Results

Ninety‐nine per cent of fracture sites of the medial wall and 100% of fracture sites of the floor were posterior to the centre of the unaffected globe. The affected globe moved significantly medially (p < 0.001) and backwards (p < 0.001) in pure medial‐wall fracture; backwards (p < 0.001) and downwards (p = 0.017) in pure floor fracture; and medially (p < 0.001), backwards (p < 0.001) and downwards (p < 0.001) in medial‐wall and floor fractures. Displacement of the globe was correlated with displacements of the orbital walls, and the regression formulae were therefore fitted. Application of the formulae revealed that the same extent of orbital wall displacement caused more displacement of the globe in female patients than in male patients.

Conclusions

A linear measuring method in a three‐dimensional co‐ordinate system was established to identify the displacements of orbital walls and the displacement of the globe in orbital blowout fractures. The regression formulae generated in this study might be used in clinical practice to predict late displacement of the globe by measuring the displacements of orbital walls.